Yes, external jumpers were not needed because all connectors were internally connected behind the plugboard. That was the default. Plugging in a cable mechanically disconnected that part of the circuit (with a simple lever mechanism) and redirected the flow of electricity through the cable. So all letters had a complete circuit whether there was a cable plugged in or not.

CAPTCHA
This question is for testing whether you are a human visitor and to prevent automated spam submissions.